Water is a sine qua non of daily life and is something we cannot live without.
Generally, tap water is gathered in a large way, purified and treated through various purification processes, and then, is supplied to households through various pipes.
In this instance, the tap water is exposed to various germs (bacteria or microorganisms) while flowing through the pipes, and hence, the tap water where germs passed through is supplied to the households.
In the case that people drink the tap water, they are safe from various germs because they drink the water after purifying or boiling the water, but when they take a shower or a bath, because they directly use the tap water without any filtering or purification process, in the case that the tap water is polluted, a user's skin is in direct contact with the polluted water and it may cause serious skin diseases.
Moreover, with development of industrials, various rare diseases have been increased, as an example, there is an atopic disease, which is one of various skin diseases, and in this case, doctors advise to always keep the moisturized skin condition and use purified water, which is not harmful to the skin.
Hence, recently, some people use a water softener installed in a bath room for skin care. However, the water softener is useful for skin care because it generates soft water, but does not provide an effect to sterilize various germs and is not useful to cure skin diseases.
Furthermore, the water softener has several problems in that an available space of the bath room decreases because it requires a space for installing the water softener in the bath room, and in that it takes much money to install the water softener in the bath room because the water softener is expensive.